Reconstructions of the southern annular mode (SAM) during the last millennium

The leading mode of atmospheric variability in the Southern Hemisphere is the Southern Annular Mode (SAM), which affects the atmosphere and ocean from the mid-latitudes to the Antarctic. However, the short instrumental record of the SAM does not adequately represent its multi-decadal to centennial-s...

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Bibliographic Details
Published in:Progress in Physical Geography: Earth and Environment
Main Authors: Hessl, A, Allen, KJ, Vance, T, Abram, NJ, Saunders, KM
Format: Article in Journal/Newspaper
Language:unknown
Published: Arnold 2017
Subjects:
ice cores
tree rings
lake sediments
corals
climate reconstruction
Southern Hemisphere climate
climate modes
Antarctic
The Antarctic
Indian
Antarc*
Sea ice
Online Access:https://eprints.utas.edu.au/43023/
https://doi.org/10.1177/0309133317743165
Description
Summary:The leading mode of atmospheric variability in the Southern Hemisphere is the Southern Annular Mode (SAM), which affects the atmosphere and ocean from the mid-latitudes to the Antarctic. However, the short instrumental record of the SAM does not adequately represent its multi-decadal to centennial-scale variability. Long palaeoclimatic reconstructions of the SAM would improve our understanding of its low frequency behavior and its effects on regional temperature, rainfall, sea ice, and ecosystem processes. In this progress report, we review three published palaeoclimatic reconstructions available for understanding multi-decadal to centennial-scale variability of the SAM. Reconstructions reviewed here show similar patterns of decadal SAM variability during the last two centuries, but earlier centuries are less coherent. Reconstructions clearly maintain similar trends towards more positive SAM states since the onset of significant anthropogenic climate forcing from rising greenhouse gas (GHG) concentrations and ozone depletion and these excursions appear unprecedented over at least the last 500 years. We describe how new multi-proxy reconstructions of the SAM could further improve our understanding of its long-term variability and effects across all geographic sectors of the Southern Hemisphere. Here, we recommend careful selection and development of proxies in SAM-sensitive regions and seasons. In particular, proxies related to cool-season conditions and from the poorly-sampled Indian Ocean sector would allow for a true circumpolar and year-round reconstruction of past SAM variability.

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